a. Field of the Invention
The present invention relates to a device for displaying a sequence of 3D images on the basis of a first sequence of source images corresponding to the left eye and of a second sequence of source images corresponding to the right eye of an observer, said source images being conveyed respectively by a video signal S.sub.1 and by a video signal S.sub.2 of respective luminous intensities E.sub.1 and E.sub.2 and either emanate from reception and/or decoding units which split the light along a first analysis path for light corresponding to the left eye and along a second analysis path corresponding to the right eye of the observer, or are produced in a manner known per se by electronic means of image synthesis.
b. Description of the Prior Art
The 3D display or stereoscopic display of images usually consists in viewing on one and the same device a series of images corresponding to the right eye and a series of images corresponding to the left eye of an observer. These two video sequences are in general captured or generated in such a way as to make it possible to comply with the geometry of human vision so that the offsets between the left view and the right view of the observer are reconstructed correctly by the psychovisual process which allows stereoscopic vision.
Among the known solutions for generating a luminous signal compatible with stereoscopic vision, the double-display or double-projection devices display the two video sequences simultaneously. The two paths are combined by polarizing one of these two paths in a first specified direction and by polarizing the other path in a second direction direction. Separation of the two paths, at the observer, is achieved by appropriate polarizing glasses. These devices have the drawback, however, of duplicating the number of image generator devices which may be, for example, television type monitors stationed symmetrically on each side of a semi-reflecting plate, so that the screens appear merged from the viewpoint of the observer. In this case, it is necessary to station a polarizing filter in front of each screen so as to create the desired polarization orientation. The image generator devices may also consist of two video projectors. In this case, it is necessary to fit out each beam with an appropriate polarizing filter. Furthermore, projection must be carried out onto a special screen so as to preserve the orientation of the polarization. This considerably raises the complexity and cost of such devices.
Other known solutions use either time-sequencing devices or spatial-interlacing devices. In the first case, the images are time-division multiplexed for example, by interlacing, on one and the same signal and at video rate, video signals corresponding respectively to the right eye and left eye of the observer. Said paths are separated in general by special glasses which block off the right eye and the left eye alternately and in synchronism with the interlacing. In a manner known per se, the blocking off of a path is achieved by stationing a liquid crystal cell between a polarizer and an analyser. The rotation (by 90.degree.) or non-rotation of the polarization by the liquid crystal makes it possible to render the glass passing or blocking at the desired rate. A major drawback of this type of device stems from the fact that the apparent frequency of display (for each eye) is halved as compared with non-stereoscopic display.
As far as the spatial-interlacing devices are concerned, they consist of micropolarizing halftone filters enabling each R, G or B sub-pixel of an image to be assigned an identified polarization direction. Multiplexing the signals S.sub.1 and S.sub.2 in tandem with the polarization frame makes it possible to generate a suitable luminous signal. In these types of device, the apparent spatial resolution (for each eye) is halved as compared with non-stereoscopic display.
The purpose of the invention is to alleviate the drawbacks of the prior art devices by means of a compact device which makes it possible to preserve the frequency of display and the resolution of the images to be displayed at least at the same level as those achieved by non-stereoscopic devices.